Surfactant is a chemical component in a hydraulic fracturing (“fracking”) fluid which is usually used to enhance initial production and to possibly improve long term production of the reservoir. Different roles that surfactant play to increase the production are decreasing capillary pressure of the fracturing fluid inside formation rocks for effective flow back, possibly emulsifying more oil globules and droplets in the reservoir and possibly changing the wettability from oil-wet to water-wet, just to name a few. There has been a new trend of using weakly emulsifying surfactant (WE) in the field over non-emulsifying surfactant (NE) as WE surfactants seems to be effective in terms of enhanced oil recovery from various liquid rich shale plays across North America.
Surfactant has proven to be critical to enhance initial production and sustain long term production in low permeability oil and gas reservoirs. During hydraulic fracturing operations, surfactants are pumped together with other chemicals to target formation zones. Once surfactants reach downhole, they can interact specifically with oil molecules, strip them off the rock and mobilize them through the reservoir. For those mechanisms to deploy, it is believed that surfactants should remain in the reservoir. To ensure optimum application of surfactants, operating and service companies have been searching for tools for tracking surfactant residuals in flow back and produced waters, which is thought to be possibly correlated with well productivity. One of the methods for determining how much surfactant is left in the reservoir is to monitor surfactant residuals in produced waters. Because of the presence of various total dissolved solids (TDS) levels and other fracturing additives such as friction reducers, scale inhibitors or biocides, it is not an easy task to track surfactant residuals. Conventional methods such as methylene blue (MB) based absorbance measurements take into account the bonding between anionic surfactants and cationic MB, but MB would bond with anything that is anionic in produced waters, resulting in erroneous analysis. Therefore, following the conventional dye based approach, such as methylene blue that typically combines with anionic surfactants, requires that the concentration of the combined complex be determined by using spectroscopic methods. This approach, however, can lead to erroneous results because of the presence of anionic friction reducers, scale inhibitor and/or gelled fluids.
It should be understood that the various embodiments are not limited to the arrangements and instrumentality shown in the drawings.